JP2016172680A - Method of sorting coal ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of easily sorting coal ash used for a coal ash-containing raw material for cement clinker high in easily burning property, based on physicochemical properties of coal ash.SOLUTION: The method of sorting coal ash is a method for sorting coal ash used for a coal ash-containing raw material for cement clinker high in easily burning property, based on a B value calculated from the following (1) formula. B=S/A+0.058×C (1), where S represents percentage content (mass%) of SiOin a glass phase in coal ash, A represents percentage content (mass%) of AlOin the glass phase in coal ash and C represents Blaine specific surface (cm/g) of the coal ash.SELECTED DRAWING: Figure 2

Description

  The present invention relates to the selection of coal ash for selecting coal ash to be used as a coal ash-containing raw material for cement clinker (hereinafter simply referred to as “coal ash-containing raw material”) having high calcination property (low-temperature calcination property). Regarding the method.

According to materials published by the Coal Energy Center, the amount of coal ash generated in 2012 was 12.66 million tons, of which 66% was used as a raw material for cement.
However, coal ash greatly varies in physicochemical characteristics such as chemical composition and particle size depending on the type of coal and combustion conditions, and affects the easy calcination of coal ash-containing raw materials. Therefore, although quality control of coal ash is required, the quality control items are not clear because the characteristics of coal ash that affect the calcination property of the coal ash-containing raw material are not known.

  For example, in the raw material for low-temperature fired cement clinker described in Patent Document 1, the coal ash used for the raw material is defined as 10% by mass or less with a particle group of 32 μm or more and an average particle size of 2 to 10 μm, and is used as a raw material. Coal ash is managed by particle size (physical properties). However, the quality control items in Patent Document 1 do not include the chemical composition or the like (chemical characteristics) of coal ash. Therefore, it is difficult to prepare a coal ash-containing raw material having high calcination property in quality control of coal ash without considering the chemical characteristics of coal ash. Therefore, a method for evaluating the calcination property in addition to the chemical characteristics of coal ash is desired.

JP, 2014-181161, A

  Therefore, an object of this invention is to provide the method which can select easily the coal ash used for the coal ash containing raw material with high calcination property based on the physicochemical characteristic of coal ash.

Therefore, in order to achieve the above object, the present inventor has intensively studied the physicochemical characteristics of coal ash that affects the flammability, and as a result, the inclusion of SiO ₂ and Al ₂ O ₃ in the glass phase in coal ash. The present invention was completed by finding that the rate (chemical characteristics) and the specific surface area (physical characteristics) of the ash of coal ash greatly affect the calcination property.
That is, the present invention is a coal ash sorting method having the following configuration.

[1] A coal ash sorting method for sorting coal ash used for a coal ash-containing raw material having high calcination property based on a B value calculated from the following formula (1).
B = S / A + 0.058 × C (1)
However, in (1), B represents an indication that easy firing of coal ash containing material, S is expressed content of SiO ₂ glass phase in the coal ash (mass%), A coal ash represents the content of _Al 2 _{O 3} of the glass phase of the inner (mass%), C represents a Blaine specific surface area of the coal ash ^(cm 2 / g).
[2] The method for sorting coal ash according to [1], wherein the coal ash having the B value of 270 or more is sorted as coal ash to be used for a coal ash-containing raw material having high calcination property.

  The method for sorting coal ash according to the present invention can easily sort coal ash used for a coal ash-containing raw material with high calcination property based on the physicochemical characteristics of coal ash.

It is the figure which showed the pattern of the calcination temperature of a coal ash containing raw material. It is a figure which shows the correlation of B value and the content rate of the free lime in a baked product. (A) Content of total SiO ₂ in coal ash, (b) Content of total Al ₂ O ₃ in coal ash, (c) Content of glass phase in coal ash, or (d) In coal ash is a diagram showing the correlation between the value of a particular formula, the content of free lime in the firing thereof, and a Blaine specific surface area of the content and coal ash of the total SiO ₂ and total Al ₂ O _3, and FIG. 2 Shown for comparison with.

The present invention is a coal ash sorting method for sorting coal ash to be used for a coal ash-containing raw material having high calcination properties based on the B value calculated from the formula (1). Hereinafter, the present invention will be described in detail.
1. (1) Formula In this invention, B value which is the parameter | index for selecting the said coal ash is calculated using said (1) Formula. In the derivation method of the equation (1), as shown in the examples described later, the content (B) of free lime in the fired product (cement clinker) is used as the objective variable, and as an explanatory variable, Multiple regression analysis is performed by using the content ratio of SiO ₂ in the glass phase, the content ratio of Al ₂ O ₃ in the glass phase in the coal ash, and the Blaine specific surface area of the coal ash to derive a multiple regression equation. Therefore, the calculated B value is a value that correlates with the content of free lime in the fired product.
The characteristics of the present invention were selected as explanatory variables: SiO ₂ content in the glass phase in coal ash, Al ₂ O ₃ content in the glass phase in coal ash, and Blaine specific surface area of coal ash. There is. The explanatory variable was found after repeatedly trying regression analysis using various physicochemical characteristics of coal ash.
For comparison, the results of regression analysis using other various physicochemical characteristics of coal ash are also illustrated in FIG. As can be seen from FIG. 3, the correlation is low compared to the B value.

2. B value The reference value for selecting the coal ash used for the coal ash-containing raw material with high calcination property is relative. First, the required free lime content (easily baked) in the fired product is determined, and further, the B value that is the reference value is determined from the value. And the coal ash which satisfy | fills this reference | standard value is sorted out as coal ash used for a coal ash containing raw material with high calcination property. For example, in the example of FIG. 2 described later, when the required free lime content in the calcined product is set to 2.25% by mass, the B value becomes 270 as the reference value, and the B value is 270 or more coal. The ash is selected as coal ash to be used as a coal ash-containing raw material with high calcination properties.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
1. Materials Used (1) Reagents Reagents used were silica (SiO ₂ ), alumina (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), calcium carbonate (CaCO ₃ ), magnesium oxide (MgO), dihydrate gypsum. (CaSO ₄ .2H ₂ O), sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), titanium oxide (TiO ₂ ), and calcium hydrogen phosphate dihydrate (CaHPO ₄ .2H ₂ O) And all the special grade reagents (manufactured by Kanto Chemical Co., Inc.) were used.

(2) Coal ash The chemical composition of the used coal ash is shown in Table 1, the mineral composition of the coal ash is shown in Table 2, and the chemical composition in the glass phase in the coal ash is shown in Table 3. In addition, Table 3 shows B values calculated based on the content values of SiO ₂ and Al ₂ O _{3 in} Table 3 and the Blaine specific surface area values in Table 1 using the formula (1).
The chemical composition of coal ash was measured using XRF (clay calibration curve method). The mineral composition of coal ash was determined based on the Rietveld method described in the following document a based on the chemical composition of the coal ash. Moreover, the chemical composition in the glass phase in coal ash was calculated | required based on the method as described in the following literature b.
Reference a: Kiyoichi Hoshino et al. “Application of X-ray diffraction / Rietveld method in the determination of cement minerals containing amorphous admixtures”, Cement and Concrete Papers, No. 59, pp. 14-21 (2005)
Literature b: Haruka Takahashi et al. “FA Characterization Using SEM-EDS / EBSD and Particle Analysis”, Taiheiyo Cement Research Report, 162, pp. 3-14 (2012)

2. Calcination of coal ash-containing raw material According to the formulation shown in Table 5 adjusted to be a cement clinker having the chemical composition shown in Table 4, the above materials were prepared to prepare a coal ash-containing raw material (pellet). Next, the coal ash-containing raw material was fired using an electric furnace under the firing conditions shown in FIG. Further, the content of free lime in the obtained fired product was measured in accordance with JIS R 5202 “Cement chemical analysis method”. The results are shown in Table 6.

  The content of free lime in the fired product is an index indicating the degree of firing (good or bad). From Table 6, the raw material 1 has the highest calcination property, and the raw material 3 has the lowest. Next, in order to confirm the ease of firing of the raw material, the raw material 1 was fired under the conditions of a firing temperature of 1420 ° C. and a firing time of 40 minutes, and the raw material 3 was fired under the same firing time of 1470 ° C. and a firing time of 40 minutes. did. As a result, the content of free lime was 0.58% by mass in the fired product of raw material 1 and the same content as 0.59% by mass in the fired product of raw material 3. This result shows that the raw material 1 needs a lower firing temperature than the raw material 3 to obtain a fired product (cement clinker) having the same degree of firing, and the easy firing property is higher than that of the raw material 3. ing.

3. Physicochemical characteristics of coal ash affecting the calcination of coal ash-containing raw materials The correlation between free lime, which is an indicator of the degree of calcination, and various physicochemical characteristics of coal ash was investigated. Specifically, regression analysis was performed using the content of free lime in the calcined product as an objective variable and various physicochemical characteristics of coal ash as explanatory variables. As a result, as shown in FIG. 2, the content of SiO ₂ and Al ₂ O ₃ in the glass phase in the coal ash (the values in Table 3 were used), and the specific surface area of the ash in the coal ash (Table 1). The value of the specific formula (B value) including the free lime content was high. And since the B value is 270 or more and the content rate of a free lime is low, for example, B value 270 or more can be selected as coal ash used for a coal ash containing raw material with high calcination property. .
For comparison, as other physicochemical characteristics of coal ash, the content of total SiO _{2 in} coal ash, the content of total Al ₂ O ₃ , the content of glass phase, the total SiO _{2 in} coal ash And the correlation with another specific formula including the content of total Al ₂ O ₃ and the Blaine specific surface area of coal ash is shown in FIG. As can be seen from FIG. 3, the correlation between these physicochemical properties and the content of free lime is lower than the correlation between the B value and the content of free lime.

Claims (2)

A coal ash sorting method for sorting coal ash to be used for a coal ash-containing raw material for cement clinker having a high calcination property based on the B value calculated from the following formula (1).
B = S / A + 0.058 × C (1)
However, (1) where, B denotes the index indicating ease firing of coal ash containing feedstock cement clinker, S is expressed content of SiO ₂ glass phase in the coal ash (mass%), A Represents the content (mass%) of Al ₂ O ₃ in the glass phase in coal ash, and C represents the Blaine specific surface area (cm ² / g) of coal ash.   The method for sorting coal ash according to claim 1, wherein the coal ash having a B value of 270 or more is sorted as coal ash to be used as a coal ash-containing raw material for cement clinker having a high calcination property.

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